The present invention relates to apparatus for establishing and maintaining a stable discharge across a stream of gas flowing through a gas-flow channel. The invention is particularly applicable to high-power flowing-gas lasers, and is therefore described below with respect to such application.
There has been considerable activity in recent years to produce high-power flowing-gas lasers for use particularly in the metalworking industries. Examples of some of the known lasers of this type are described in U.S. Pat Nos. 3,641,457; 3,702,973; 3,748,594; 3,758,874; 3,886,481; 3,021,098; 4,058,778; 4,317,090; and 4,321,558. One of the main problems in the design of such high-power lasers is the dissipation of the heat, since power lasers cannot operate efficiently at unduly high temperatures; for example, the CO.sub.2 laser, which is the one mainly used today for high power applications, cannot operate efficiently at temperatures much above 200.degree. C. Another problem in the design of high-power lasers is the difficulty in establishing and maintaining a stable electrical discharge across the stream of flowing gas. U.S. Pat. Nos. 3,748,594 and 3,758,874 of those cited above are particularly directed to this problem. It will be appreciated that both of the above problems involved in the construction of high-power flowing-gas lasers are also involved in the design and construction of other high-power flowing-gas electrical devices.